The invention relates to (alkyl,bromo)phenoxy alkyl (meth)acrylate monomers and polymers made therefrom.
Reactive chemical monomers can be used to prepare polymeric materials which have various properties and which are useful for various applications. As one example, monomers having optical properties can generally be used, alone or in combination with other reactive materials, to produce useful products having a high index of refraction, and that are useful to control the flow and intensity of light. To continually improve such products, or the processes for preparing such products, there is an ongoing need to develop new and improved high index of refraction monomeric materials.
Some brominated aromatic (meth)acrylate monomers have been found to be useful as high index of refraction monomers. These monomers can exhibit desirable optical qualities, but generally tend to display relatively high melting points, and therefore exist as solids at temperatures near room temperature (e.g., in the range from about 20 to 30 C.). Often such known brominated monomers have melting points significantly above room temperature. In addition, polymerization of these monomers (by themselves or with other comonomers) can frequently lead to a polymer with a relatively high glass transition temperature (Tg) which can limit the range of application of such monomers.
It would be desirable to identify monomers useful to produce optical materials, where the monomers have physical properties including a relatively high index of refraction, a relatively low melting point in combination with a relatively low room temperature viscosity, and which can be used to prepare polymers (e.g., homopolymers or copolymers) having a relatively low Tg.
The invention provides (alkyl,bromo)phenoxy alkyl (meth)acrylate monomers. The term (alkyl,bromo)phenoxy alkyl (meth)acrylate is used herein to refer to chemical compounds comprising a (meth)acrylate, a phenoxy ring substituted with at least bromine and an alkyl group, and a divalent alkylene group connecting the (meth)acrylate to the phenoxy ring. Preferred monomers exhibit a relatively high index of refraction; i.e., at least 1.50. Preferred monomers also have a relatively low melting temperature; i.e., below about 60 degrees celsius (60 C.), more preferably below about 35xc2x0 C. or 30xc2x0 C., and most preferably exist as a liquid at or near normal room temperature (e.g., 25 C.). In addition, preferred monomers have a relatively low room temperature viscosity, and can be polymerized, either alone or in combination with one or more other comonomers, to prepare polymers with a relatively low glass transition temperature (Tg), e.g.,  less than 50 C.
An aspect of the invention relates to (alkyl,bromo)phenoxy alkyl (meth)acrylate monomers such as those having the general formula: 
wherein m is from 1 to 4; R2 is hydrogen or methyl, R1 is a straight or branched alkyl having at least two carbon atoms, and L is a straight or branched alkylene.
Another aspect of the invention relates to a polymerizable composition containing an (alkyl,bromo)phenoxy alkyl (meth)acrylate monomer such as that defined directly above. The polymerizable composition can further contain one or more other comonomer.
Yet another aspect of the invention relates to a polymer or polymeric material comprising a chemical segment having the formula: 
wherein m is from 1 to 4, R2 is xe2x80x94H or methyl, R1 is a straight or branched alkyl having at least two carbons, and L is a straight or branched alkylene. Such a polymer can be prepared by polymerization of the (alkyl,bromo)phenoxy alkyl (meth)acrylate monomer.
As used within the present description, xe2x80x9cmonomerxe2x80x9d refers to a monomer on an individual (i.e., molecular) scale, and also to a composition of such monomers on a macroscopic scale such that the composition can be described as having a physical state of matter (e.g., liquid, solid, etc.) and physical properties (e.g., melting point, viscosity, glass transition temperature (of a polymeric form), and index of refraction).
xe2x80x9cIndex of refraction,xe2x80x9d or xe2x80x9crefractive index,xe2x80x9d refers to the absolute refractive index of a material (e.g., a monomer), which is understood to be the ratio of the speed of electromagnetic radiation in free space to the speed of the radiation in that material, with the radiation being of sodium yellow light at a wavelength of about 583.9 nanometer (nm). Index of refraction can be measured by known methods, and is generally measured using an Abbe Refractometer.
xe2x80x9cGlass transition temperature,xe2x80x9d (Tg), is the temperature range over which a thermoplastic polymer changes from a brittle, glass state to a plastic state. Tg can be measured by methods known in the analytical chemistry art, such as the method described in the Examples section below.
xe2x80x9c(Meth)acrylatexe2x80x9d refers to both acrylate and methacrylate compounds.